   Then get or generate some text or HTML code and return it.

        >>> def my_url_handler(url, content_type):
        ...     text = 'the URL sent was: (%s, %s)' % (url, content_type)
        ...     return text

        Start server thread on port 0.
        If you use port 0, the server will pick a random port number.
        You can then use serverthread.port to get the port number.

        >>> port = 0
        >>> serverthread = pydoc._start_server(my_url_handler, port)

        Check that the server is really started.  If it is, open browser
        and get first page.  Use serverthread.url as the starting page.

        >>> if serverthread.serving:
        ...    import webbrowser

        The next two lines are commented out so a browser doesn't open if
        doctest is run on this module.

        #...    webbrowser.open(serverthread.url)
        #True

        Let the server do its thing. We just need to monitor its status.
        Use time.sleep so the loop doesn't hog the CPU.

        >>> starttime = time.monotonic()
        >>> timeout = 1                    #seconds

        This is a short timeout for testing purposes.

        >>> while serverthread.serving:
        ...     time.sleep(.01)
        ...     if serverthread.serving and time.monotonic() - starttime > timeout:
        ...          serverthread.stop()
        ...          break

        Print any errors that may have occurred.

        >>> print(serverthread.error)
        None
   r